Motor stator using corner scraps for additional electrical components

ABSTRACT

A method for making a motor and auxiliary devices with a unified stator body comprises providing a piece of material ( 10 ) having an area larger than a cross section of the stator ( 11 ), removing material from the piece of material ( 10 ) to form a pattern for a cross section of a core ( 11 ) for the stator, and removing material from the piece of material ( 10 ) outside the cross section of the core of the stator ( 11 ) to allow positioning of cores ( 22, 23, 24 ) for supporting windings ( 25, 26, 27 ) of least one additional electromagnetic device, such as a transformer ( 62 ) in a dc-to-dc converter ( 61, 62 ) that provides a low voltage dc output. An article of manufacture made according to the invention is also disclosed and apparatus made with the method and article of manufacture are also disclosed.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH

[0001] This invention was made with assistance under Contract No.DE-AC05-00OR22725 with the U.S. Department of Energy. The Government hascertain rights in this invention.

BACKGROUND OF THE INVENTION

[0002] The field of the invention is motors, and in particular examplesdescribed herein, motors of a type operated under PWM inverter motorcontrol, including induction motors, brushless dc motors, andsynchronous ac motors.

[0003] A motor can be excited in an ac induction mode, ac synchronousmode, or brushless dc (BLDC) mode using a dc link inverter to controlthree-phase switching of current in the windings of a 3-phase motor.

[0004] The increasingly sophisticated application of the contemporarytechnology often calls for several electromagnetic devices to be usedsimultaneously. For example, when an electric motor drive is used in aremote situation, various associated devices such as the auxiliary powersystems, filters, transformers, and chokes may also be required. Thiscreates an opportunity for cost reduction by forming multiple devicesfrom individual components.

SUMMARY OF THE INVENTION

[0005] The present invention provides a method, an article ofmanufacture and an apparatus which utilizes corner scraps of statorlamination pieces of a motor to form magnetic cores for additionalelectromagnetic devices. Such devices can include, but are not limitedto, DC-DC converters, transformers, filter chokes, AC output powersupplies, and smoothing filters for the main stator windings in PWMapplications. The corner cores are used for the magnetic cores of theseassociated devices.

[0006] The flux paths and the flux frequencies in the corner material ofthe present invention are different from those used in the conventionalstators, such as the square stator lamination punching of awashing-machine motor. The stator portion of the punching of awashing-machine motor carries only the fundamental-frequency rotatingflux. The corner cores of this invention share magnetic paths with thestator back iron.

[0007] In the present invention at least one auxiliary component can beadded in each corner of the stator, and the auxiliary devices can beeither single-phase or multiple phase components.

[0008] The invention maintains the original motor core length.

[0009] The invention may be applied to induction motors, brushless dcmotors, wound-field synchronous motors and permanent-magnet (PM) motors.

[0010] The invention may be practiced with 2-phase modulation whichlowers the switching losses of the main inverter.

[0011] Other objects and advantages of the invention, besides thosediscussed above, will be apparent to those of ordinary skill in the artfrom the description of the preferred embodiments which follows. In thedescription reference is made to the accompanying drawings, which form apart hereof, and which illustrate examples of the invention. Suchexamples, however are not exhaustive of the various embodiments of theinvention, and therefore reference is made to the claims which followthe description for determining the scope of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012]FIG. 1 is a plan view of a first embodiment of a stator laminationpunching with additional apertures cut out of each of the four sections;

[0013]FIG. 2 is a plan view of a second embodiment stator laminationpunching with four portions cut out of each of the four corner sections;

[0014]FIG. 3 is an electrical schematic diagram of a motor, an inverterand an auxiliary power system constructed with the stator laminationpunching of FIG. 1;

[0015]FIG. 4 is a graph of current vs. time for dc charging currentwaveforms in the apparatus of FIG. 3 for a 2-phase modulation; and

[0016]FIG. 5 is a graph of current vs. time for dc charging currentwaveforms in the apparatus of FIG. 3 for a 3-phase modulation.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] Referring to FIG. 1, the present invention is practiced in amethod for making a stator lamination 10. The stator lamination 10 inthis embodiment is square, but in other embodiments it could berectangular or another nonrectangular shape. Within the square is acircular section 11 defined by a stator radius 15 that originates at ageometric center 12 of the lamination 10. A large central opening 13 isformed in the lamination 10 by cutting out a circular portion. Thestator portion 11 of the lamination has slots 14 punched along radii 15from the center 12 and opening into the central opening 13 throughnarrow slits 16 separating tooth pieces 17. Stator windings (not shown)would be positioned in the slots 14 according to a winding pattern.

[0018]FIG. 1 shows an example of using corner scraps of a statorpunching to form cores for auxiliary devices. In the upper left corner,three pieces are cut out of the lamination 10 to form four apertures 18,19, 20 and 21. The legs 22, 23 and 24 formed between the apertures 18,19, 20 and 21 are used as cores for the auxiliary devices. Windings 25,26 and 27 are positioned around the cores 22, 23 and 24. The threewindings may be used in three single-phase devices, or in two-phase orthree-phase devices.

[0019] In the lower left hand corner, as well as the other two corners,two pieces are cut out to form two apertures 28, 29 and a single leg orcore 30. A transformer coil 31 with a primary coil 33 overlapping asecondary coil 32 is positioned around the leg 30. Similarly, thewindings 25, 26 and 27 may be double windings with a primary windingoverlapping a secondary winding, but due to considerations of space andclarity only one of the windings is shown in the upper corner 35 inFIG. 1. However, if the corner device is a choke, a secondary winding isnot required. The device in the lower left corner 36 is an example of asingle phase device, whereas the upper corner provides cores for athree-phase device. The number of legs and the flux pattern in eachcorner section 35, 36, 37 and 38 may be varied to obtain the functionsof the desired auxiliary devices.

[0020]FIG. 2 shows another example of a stator lamination 40 usingcorner punchings in a stator punching to provide a 3-leg shell-typepattern 41, 42, 43, 44 for all corners 45, 46, 47 and 48. Because thestator slots 49 are occupied solely by the original motor windings andthe stator back iron (or yoke) magnetic path is only partially sharedwith the corner cores 51, 52, 53, the length of the stator core can bemaintained as that of the original motor.

[0021] As an example of the utilization of the corner cores for theassociated devices and the differences from those of a conventionalsquare punching, an auxiliary power system that operates simultaneouslywith the motor under independent control is illustrated as follows.

[0022]FIG. 3 shows an example of a motor control circuit having aninverter 60 and a dc-to-dc low voltage output power converter 61, 62.For an auxiliary power device there are three basic functions. In orderto convert energy from a dc voltage source to a different-voltageauxiliary dc power, there must be a switching function that changes dcto ac, a transformer function that steps down or steps up the acvoltage, and a rectifier function that converts ac to dc. The powerswitching devices 63, 64, 65, 66, 67, 68 of the three legs of the maininverter 60 produce adjustable currents in the motor main windings (notshown) as well as the controllable zero-sequence-switching currents inthe three transformers 62 a, 62 b, 62 c for the auxiliary converter 62for a different-voltage power output at output terminals 69. Only onepower-switching device (such as an IGBT) for each auxiliary voltageoutput 69 is required in this arrangement. This is because the circuitutilizes the zero-sequence switching of the switching devices 63-68 ofthe main inverter. The functions of the three transformers 62 a, 62 b,62 c in the converter 62 can be provided by the corner cores seen inFIGS. 1 and 2. The transformers 62 a, 62 b, 62 c provide for steppingup, or in this case, stepping down of the ac voltage of thezero-sequence switching currents. These voltages are then rectified bythe rectifier 61.

[0023]FIG. 4 shows the dc charging current waveforms of the system shownin FIG. 3 at 100, 55, and 0 Ampere, respectively, under a full 2-phasemodulation.

[0024]FIG. 5 shows the dc charging current waveforms of the circuitshown in FIG. 3 at 102 and 0 Ampere, respectively, under a conventional3-phase modulation. The two-phase modulation of FIG. 4 lowers theswitching losses in the inverter 10, but may provide less than a 100%duty cycle.

[0025] It can be seen from this example that the flux paths and the fluxfrequencies in the corner cores of this invention are different fromthose used in a conventional motor, such as the square stator punchingof a washing-machine motor. The latter punching carries only thefundamental-frequency rotating flux.

[0026] There are many other examples of electromagnetic devices that mayuse the corner cores of the present invention, including but not limitedto dc-to-dc converters, transformers, filter chokes, ac output powersupplies, and smoothing filters for the main stator windings in PWMapplications.

[0027] In the method of the present invention a piece of ferromagneticsheet material 10 is provided with an area that is larger in crosssection than the cross section 11 of the stator. Material is removedfrom the sheet material 10 to form the central opening 13 and the slots14 to form the stator. Material is also removed from the corner sections35, 36, 37 and 38 to form the corner apertures 18, 19, 20 and 21 in FIG.1, for example. Individual pieces of sheet material 10 are assembled toform a stator core and the legs 22, 23 and 24, which will provide coresfor an additional electromagnetic device. Coils 25, 26 and 27 areassembled to the legs 22, 23 and 24 to form a 3-phase device of the typeseen in FIG. 3. Although windings 25, 26 and 27 are represented onlygenerally, these could include both primary and secondary windings asseen for element 31. In the other corner sections 36, 37 and 38, singlephase devices can be formed. FIG. 2 provides an embodiment in which allfour corner sections 45, 46, 47 and 48 can accommodate 3-phase devices.

[0028] The process preferred for removing pieces is material is punchingor stamping, but cutting and other methods may be used. Typically thesheet material 10 is an iron alloy of a type recommended for use inferromagnetic applications.

[0029] Although the description of detailed examples was given onpunchings, this invention can be used for the compressed powder coresthat are not made of lamination punchings.

[0030] In an additional sequence for allowing insertion of the coilsinto the corner cores, portion(s) of the corner cores 22, 23 and 24 canbe removed and the coils 25, 26 and 27 placed around the cores 22, 23and 24 and the small subassemblies re-assembled with the stator core.

[0031] It is also possible to use different materials to form the cornercore. For example the removable portion(s) of the corner core can bemade of compressed powder of metallic and other particles, which resultsin a core with ferromagnetic properties, and the main core can be madeof punchings.

[0032] This has been a description of detailed examples of theinvention. It will apparent to those of ordinary skill in the art thatcertain modifications might be made without departing from the scope ofthe invention, which is defined by the following claims.

We claim:
 1. A method for providing a stator of a motor, as well asproviding cores for at least one additional electromagnetic device, themethod comprising: providing a piece of material having an area largerthan a cross section of the stator; removing material from the piece ofmaterial to form a pattern for a cross section of a core for the stator;removing material from the piece of material outside the cross sectionof core of the stator to allow positioning of at least a portion of atleast one core for at least one additional electromagnetic device withinthe piece of material.
 2. The method of claim 1, wherein the material isremoved to form the core of a single-phase device.
 3. The method ofclaim 1, wherein the material is removed to form the core of amultiple-phase device.
 4. The method of claim 1, wherein material isremoved from corner sections outside the cross section of the core ofthe stator to provide cores for a plurality of additionalelectromagnetic devices.
 5. The method of claim 1, wherein the piece ofmaterial is a sheet of material.
 6. The method of claim 2, wherein thematerial is an iron alloy.
 7. The method of claim 1, further comprisingassembling the piece of material with other pieces of material of likeconfiguration to form cores for a stator and for at least one additionalelectromagnetic device.
 8. The method of claim 7, wherein the stator isa stator in a motor of the type operated under PWM control, and whereinthe electromagnetic device is an AC step-down transformer.
 9. The methodof claim 7, wherein the stator is a stator in a motor of the typeoperated under PWM control, and wherein the electromagnetic device is atleast one of: a DC-DC converter, a transformer, a filter choke, an ACoutput power supply, and a smoothing filter.
 10. The method of claim 1,wherein the portion of the core for at least one additionalelectromagnetic device is removed from the piece of material, isassembled into the electromagnetic device and is re-assembled with thepiece of material forming the stator.
 11. The method of claim 1, whereina core for at least one additional electromagnetic device is assembledinto the electromagnetic device and is then positioned within the pieceof material forming the stator.
 12. The method of claim 11, wherein thecore is made of a compressed powder material.
 13. An article ofmanufacture formed from a sheet of ferromagnetic material, said sheet offerromagnetic material having a center, having an opening formed aroundthe center, having slots formed along radii from the center, havingextending sections lying outside a circular center section of the sheetmaterial and having a plurality of apertures formed in at least one ofthe extending sections, said apertures being spaced apart for bounding acore for an electromagnetic device positioned outside said slots butwithin an outer boundary of the sheet of ferromagnetic material.
 14. Thearticle of manufacture of claim 13, wherein the plurality of aperturesincludes three apertures in one of the extending sections for forming acore of a three-phase electromagnetic device.
 15. The article ofmanufacture of claim 13, wherein a plurality of apertures is formed in aplurality of the extending sections.
 16. The article of manufacture ofclaim 15, wherein the plurality of apertures includes three apertures inone of the extending sections for forming a core of a three-phaseelectromagnetic device.
 17. An electrical motor apparatus comprising: abody of ferromagnetic material; a stator core for a motor formed in saidbody of ferromagnetic material, said stator core having a centralopening for receiving a rotor, and having slots formed along radii froma center of the body to receive windings and to define stator poles; andat least one electromagnetic core for an electromagnetic device disposedin a portion of the body lying outside of the stator core.
 18. Theapparatus of claim 17, wherein the core is a core for a single-phasedevice.
 19. The apparatus of claim 17, wherein the core is a core for amultiple-phase device.
 20. The apparatus of claim 17, wherein cores areprovided in respective outlying sections for a plurality of additionalelectromagnetic devices.
 21. The apparatus of claim 17, wherein thestator core and the electromagnetic core are formed of a plurality ofpieces of sheet material laminated together.
 22. The apparatus of claim17, wherein the stator is a stator in a motor of the type operated underPWM control, and wherein the electromagnetic device is an AC step-downtransformer.
 23. The apparatus of claim 17, wherein the stator is astator in a motor of the type operated under PWM control, and whereinthe electromagnetic device is at least one of: a DC-DC converter, atransformer, a filter choke, an AC output power supply, and a smoothingfilter.
 24. The apparatus of claim 17, wherein the electromagnetic corefor an electromagnetic device is made of a compressed powder material.